News reports quoted American military sources as saying at least four crewmembers were aboard. A news release said initial reports indicate the crash occurred in severe weather near Ghazni, about 100 miles southwest of the Afghan capital of Kabul.

The helicopter was one of two Chinooks returning to Bagram Air Base from a routine mission in southern Afghanistan when, according to a command spokeswoman, air-traffic controllers lost contact with the aircraft.

The second helicopter returned to base safely, officials said. A recovery operation is under way at the site, providing security and accounting for the dead.

The names of the dead are being withheld until their families are notified. An investigation into the cause of the crash has begun.